Family Simuliidae - Black Flies

Buffalo Gnats

Various colorful terms best not repeated in the presence of children...

BUFFALO GNAT: hump-backed appearance resembles a buffalo; may also suggest that it was originally a pest of buffalo on the great plains

adult length 2-5 mm

Adult: black to various shades of gray or yellow; thorax shiny, strongly convex, giving a humpbacked, gnat-like appearance; wings clear, broad, without hairs or scales; heavy veins near anterior wing margin, weak veins posteriorly; small head with large round eyes and short 11-segmented antennae; ocelli lacking

Larva: brown, gray, or black with light brown head; body cylindrical, somewhat club-shaped; head with prominent pair of mouth brushes used for filtering food from the water

most of North America, including the arctic

larvae develop in running water of all types, from the smallest seepages and streams to the largest rivers and waterfalls; they attach themselves to underwater rocks and other objects by means of small hooklets in a sucker-like disc at the tip of the abdomen

adults may be present spring through fall but usually for a shorter duration in a specific location, depending on species and latitude

larvae filter small aquatic organisms and detritus from flowing water

adults of many species feed on the blood of birds; a number of species do not take blood meals; only a few species attack humans, usually when a more suitable host is not available

most northern species have one generation per year; some species have multiple generations; overwinters as either an egg or a larva, depending on species and/or latitude

Below are selected quotes from an Agriculture Canada pamphlet [publication 1499] named Black Flies (1973).

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Black flies attack massively and viciously or in such small numbers that they are scarcely noticeable. They bite quietly and painlessly so that you may not be aware of having been attacked until small droplets of blood start oozing from your skin. Black flies often crawl into your hairline or through openings in your clothes before they bite you. Therefore, the bites are usually behind your ears, around your neck and beltline, and on the lower parts of your legs.

A typical black-fly bite consists of a round, pink, itchy swollen area, with a droplet of fresh or dried blood at the center. When the blood is rubbed away, a minute subcutaneous hemorrhage is visible. This hemorrhage and the surrounding pink area become diffuse and larger, and then disappear within a few days. Itching may continue intermittently for weeks, whenever the bitten area is rubbed. Scratching may cause severe secondary skin infections.

Toxins injected during an extended severe attack can cause a general illness sometimes called black-fly fever, characterized by headache, fever, nausea, and swollen, painful neck glands.

Attacks occur throughout late spring and early summer or sometimes throughout the entire summer.

Black flies attack most severely about sunrise and again at sunset.

biting midges (Ceratopogonidae)